Potential Use of Natural Red Mud as Pozzolan for Portland Cement

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Red mud, the main waste generated in aluminum and alumina production by the Bayer process, is consideredhazardous due to its high pH, according to the Brazilian standard NBR 10004/2004, and worldwide generation ofthis waste exceeds 117 million tons/year. In this work, non-calcined red mud was used, thus requiring less energyand time and reducing costs, which is the ideal condition for reusing wastes. Mortars containing 30 wt. (%) ofcement substituted by red mud showed higher strength of hardened products. The pozzolanic activity index wasevaluated based on physical and mechanical parameters (Brazilian NBR 5751 and NBR 5752 standards) and on achemical analysis (European EN 196-5 standard). A comparison of the reference mixture (without red mud) andthe results obtained with red mud confirm the potential of non-calcined red mud for use a as pozzolanic additivein cementitious materials. The setting time (according to the MERCOSUL NM 65 standard) tends to increasebut workability remains almost unchanged.